This invention relates to methods and apparatus for making photographic prints from negatives or from slides and, more particularly, relates to a method and apparatus for locally correcting the density and/or contrast of photographic negatives or slides prior to making the print to correct for localized areas of over- or underexposure in the negative or slide.
Oftentimes, when a photograph is taken, due to the conditions at the time the photograph is taken, there will be areas on the film negative produced after developing the film that are over- or underexposed relative to what can be reproduced on a photographic print. If the negative is printed using normal techniques, the photographic print will have areas where the image is either too light or too dark to be reasonably visible or aesthetically pleasing to the photographer. The overall density of the print can be corrected by changing the exposure time in printing the negative; however, this has a uniform effect over the entire print area with the result that, if the exposure time is decreased to "brighten" the print exposure from dark areas of the negative, it will result in an overexposure of the normal areas to the point where they are washed out. On the other hand, if there are overexposed areas on the negative, an increase in exposure time during printing to draw out the detail in these overexposed areas then can result in the normally exposed areas of the film producing print portions that are too dark to see otherwise visible detail.
It is known in the photographic industry to use techniques known as "dodging" or "burning" in which a density mask is built up using pieces of film or other material that are then held in the exposure path when the print is being made to adjust for the over- or underexposure of certain areas of the film. However, this technique is difficult to uniformly perform on a repeated basis because of the inherent inaccuracies in placing the density mask in the proper location each time the print is made and necessitates a greater amount of time to adjust from print to print. Also, the results of the process are not known until after the print is made and if the results are unsatisfactory, another attempt must be made in a trial-and-error method until the satisfactory result is obtained.
It is, therefore, an object of the present invention to provide a method and apparatus for producing a photographic print from a negative or slide in which areas of over- and underexposure can be locally corrected without the necessity for manually placing a density mask in particular areas of the optical path. It is a further object of this invention to provide a local density correction mask that can be adjusted on a localized-area basis prior to making the print with real-time control and observation of the result to avoid trial-and-error techniques in printing. Another object of the invention is to provide a locally variable color mask that can be used with variable-contrast paper to locally adjust the contrast of the resulting photographic prints.